This invention relates to improvements in cutting a continuous rod of material into lengths, and more particularly to cutting an advancing cigarette rod into uniform lengths.
Commercial devices for forming cigarettes, filters for smoking articles, and similar products are known. These devices typically include a cut-off device for severing a continuous rod of advancing material into lengths. The lengths are then used to form the finished product, for example, cigarettes.
One such cut-off device is that found in a cigarette "maker" machine manufactured by Molins Limited, London, England, under the trade name models Mark 9Y or Mark 9-5. The cut-off device is located downstream of the point where the advancing cigarette rod is continuously formed and includes a rotating wheel including one knife blade, an oscillating ledger, a rotating sharpening stone, and an orbiting deburring stone. The wheel rotates in a first plane that is at an acute angle relative to the advancing rod. The knife is mounted on the wheel periphery so that the blade is fixed in a second plane at an angle to the first plane. The ledger device contains an aperture through which the tobacco rod advances and a slot that is perpendicular to the longitudinal axis of the rod and surrounds the aperture. The ledger device oscillates along the advancing rod in a timed relationship to the rotation of the cut-off wheel and the speed of the advancing tobacco rod.
In operation, for each revolution of the wheel, the knife blade edge is sharpened on one side, deburred on the other side, and passed through the ledger slot and the tobacco rod as the ledger is advancing with and at the same speed as the tobacco rod, thereby severing the tobacco rod. The blade edge is curved and the cutting point of the blade moves along the blade edge as the blade passes through the rod. Thus, as the blade passes through the slot, the cutting point moves in a plane normal to the axis of the rod and that normal plane advances with the rod at the same speed as the rod and the ledger. This forms a vertical cut in the rod.
The sharpening step involves passing one side of the blade cutting edge along the surface of a revolving sharpening stone. The stone is fixed in a position in the path of the knife blade and is driven by a series of gears, belts, and pulleys powered by the maker drive mechanism in a timed relationship to the speed of the rotating wheel.
The deburring step is accomplished by passing a deburring stone along the other side of the blade cutting edge. The deburring stone freely rotates about an axis and "precesses" in an orbit about a second axis. The deburring stone moves faster than the blade and its orbit intersects the plane of the rotating knife so that the deburring stone runs away from the knife blade in contact with and along the curved cutting edge of the blade.
The deburring stone orbit is controlled by a mechanical device referred to as the orbiter. The orbiter includes a series of gears, including very fine pitch gears, and belts, connected to the maker machine drive. Thus, the orbit of the deburring stone is mechanically linked to the rotation of the cut-off wheel for deburring the other side of the blade cutting edge on each revolution.
The angular relationship of the knife blade cutting edge relative to the axis of the cigarette rod may be adjusted to cut the rod into different size lengths. Typically, the positions of the sharpening stone and the deburring stone must be moved as the plane in which the cut-off wheel rotates and the plane in which the is blade fixed relative to the wheel are adjusted for cutting different lengths.
These cut-off devices are capable of producing as many as 5,000 cigarette lengths per minute. However, these devices suffer from a wide variety of problems that require shutting down the cigarette maker machine to correct. This entails substantial amounts of down time not only to repair problems as they occur, but to restart the cigarette maker machine. The latter step involves substantial wastage of time, tobacco and cigarette paper as the maker machine must be cleaned, rethreaded with paper, and restarted to form the tobacco rod before production of cigarettes can resume. In addition, these machines are typically operated at a speed that is less than capacity because of the level of vibrations and wear experienced when operated at maximum speed.
One problem with the prior known devices is that the orbital devices are mechanically complicated, leak oil, generate heat, and introduce vibrations in the cigarette maker machine. In addition, the orbit must be carefully adjusted to the movement of the blade to effect the deburring operation. This process is difficult and requires significant amounts of time.
Further, during the cutting operation, substantial amounts of tobacco dust are generated and accumulate on the oil that has leaked on and around the orbiter mechanism. It is not unknown for fires to start in the cut-off device as a consequence of the accumulated oil and tobacco particles being ignited by heat or sparks caused by the sharpening or deburring operations. Also, the oscillatory nature of the orbiter, and its drive mechanism connected to the machine drive, introduce substantial vibrations that accelerate wear of the various moving parts.
Another problem with the known devices is that they are not readily adaptable to providing cut-off wheels with more than one blade. In particular, the orbital device would have to be regeared to obtain an orbital speed that will contact and debur each blade, thus introducing additional heat, lubrication and vibration problems.
Another problem with the prior known devices is that the sharpening stone is driven by belts and pulleys from the machine drive. Thus, the speed at which the stone rotates is controlled by the operating speed of the machine, and can be otherwise changed only by altering the gear ratios. Further, the belt and pulley drive mechanism introduces an added source of heat, wear, and potential breakage requiring shutting down the machine for service.
Accordingly, there is a continuing need for improvements in the construction and operation of devices for cutting continuously advancing rods into uniform lengths that improve the reliability, serviceability, and performance of such devices.
It is, therefore, an object of this invention to provide a sharpening stone that is independently driven for sharpening one side of each knife blade on each revolution of the blade. It is another object to provide a sharpening stone drive mechanism that is decoupled from the maker and requires minimal service.
It is another object of this invention to provide a method and apparatus for deburring a rotating knife blade without using a mechanically complicated orbital deburring device. It is another object to provide a deburring device that uses a minimum number of moving parts. It is another object to provide a deburring device that is simple to adjust. It is another object to provide a deburring device that can debur more than one knife blade. It is another object to provide a deburring device that is decoupled from the angle of travel of the knife blade.
It is another object of this invention to reduce substantially the number of mechanical parts and interconnections in the cutoff device of a cigarette maker machine. It is another object to provide a cut-off device having reduced wear and maintenance problems.
It is another object of this invention to modify a conventional cigarette maker machine and provide a cutoff device with a cutoff wheel having a plurality of blades. It is another object to provide a cutoff wheel having a plurality of knife blades that are sharpened on one side and deburred on the other side during each revolution. It is another object to provide a cutoff wheel having a plurality of blades that operates at a slower speed with fewer vibrations while maintaining the same production rate to extend the machine lifetime between service. It is another object to provide a cut-off wheel having a plurality of blades that does not require regearing of a deburring orbital device.